1. Field of the Invention
The present application relates to variable counterweighted take-up assembly for endless conveyors and endless conveyor system incorporating such take-up assembly. The invention also relates to endless conveyors incorporating such variable counterweighted take-up assembly. Although all types of endless conveyors are included, conveyors having a helical belt path are particularly contemplated.
2. Description of the Related Art
Endless conveyors of the type contemplated herein generally include an endless conveyor belt which has sufficient flexibility to allow the belt to traverse an endless path from a product input station to a product discharge station, and thereafter to return from one station to the other via a return section. When the conveyor path is straight, the belt must be capable of flexing along an axis generally perpendicular to the path. When the path is other than straight, such as a helical path of the type contemplated herein, the belt must be capable of flexing at least to a limited extent along at least three mutually orthogonal axes in order to permit the belt to traverse such relatively complex paths.
In order to permit such multi-directional flexing, such conveyor belts are generally constructed of a plurality of interconnected links which permit at least limited link-to-link articulation along two or more mutually orthogonal axes. In such instances, the links are generally constructed of a material such as steel making the weight of the belt a relatively significant factor in operating the conveyor system.
Conveyor belts of the type contemplated herein generally range from about 12 inches to about 60 inches in width and from about 200 feet to about 2,500 feet in length, and even up to about 3,000 feet in some instances. When a conveyor belt is constructed of numerous interlocked steel links and is between 10 and 60 inches in width and more than 200 feet in length, the weight of the belt becomes a significant factor to reconcile. For example, the belt must be driven through the work path which begins at the product input station and ends at the product discharge station. Thereafter, the belt enters the return section where it reverses direction and re-enters the product input station to continue operating in its endless path. In helical conveyors, the belt is driven up a helical shaped path in an up-go conveyor, and down a helical shaped path in a down-go conveyor. The belt is generally driven by friction forces imparted to it along the inner edge by a circular shaped rotating cage around which the belt is wrapped in the work zone, and it is provided with additional assistance by a motor driven sprocket which is constructed to engage the links of the belt directly as it is rotatably driven by the assist motor. Such motor assist is particularly needed in up-go helical conveyors where the relatively heavily weighted belt is made to traverse an up-go helical path against the force of gravity. A motor driven assist sprocket is also utilized in helical shaped down-go conveyors, although the gearing and roller arrangements differ somewhat from the up-go conveyors, and the assist force required is somewhat different. In other applications, the work zone of the conveyor path is straight.
Conveyor belts of the type contemplated herein are generally used for conveying products under various conditions. For example, in some applications, the belts are used to convey dough products through relatively high temperature atmospheres in order to assist the dough in rising prior to formation of a bread product. In other applications, the belts may be made to carry food products through relatively cold atmospheres, sometimes under freezing conditions. In still other applications, the belts may be required to conduct products at room temperature.
In each instance, the belt, being made of a plurality of interlocked metal links, will react to the surrounding conditions such as temperature, cleanliness and the like, with the result that the belt will undergo a natural stretch or compression such factors will, in turn, affect the belt tension. In some instances, the belt will become longer during operation and, in others, the belt may become shorter, and such variations in these vital parameters have necessitated the incorporation of a take-up section in the belt return section of the system in order to permit the accumulation of excess belt and to accommodate the increases and decreases in the length of the belt. Further, since the belt is constructed of numerous interconnected links, variations in the link-to-link spacing at any given time will also accumulate to change the overall length of the belt.
In helical conveyors, the belt will undergo compression along the inner edge of an arcuate turn and stretch along the outer edge, thus resulting in relatively complex changes in the overall conditions such as tension and length of the belt. These changes have also been found to affect the overall tension in the belt throughout the system, with the result that in some instances, particularly where sanitary conditions are not observed, the belt tension will differ between separate locations along the path.
It has been found that ideally, belt tension should be maintained as uniform as possible, and this objective has often been met with some success in the past by incorporating a take-up section in which excess belt is permitted to accumulate. In the take-up section, the excess belt is made to pass through two adjacent sections, a first fixed section and a second variable section. In the first fixed section, a portion of belt is maintained in the form of a vertical curtain of fixed length and weight. In the second variable section, the excess belt is looped under and about a floating dancer roller so as to assume a generally V-shaped configuration, and is permitted to increase and decrease in dependence upon increases or decreases in the length of the belt as may be caused by operating conditions. The weight of the portion of belt in the second variable section belt is maintained in counterbalance relation to the weight of the curtain of belt in the first fixed section such that when the length and weight of the belt in the second fixed section increases, the dancer arm moves to its lowermost position, and when the length and weight of the belt in the second variable section decrease, the dancer arm moves upwardly toward its uppermost portion.
In order to maintain a proper balance between the portions of belt in the first fixed and second variable sections, prior art systems have attached a fixed weight to the dancer arm in the second variable section. The weight is intended to complement the weight of the belt portion therein and to counterbalance the weight of the vertical curtain of belt in the first fixed section. It can be readily appreciated that a balanced or unbalanced condition between the two sections will in turn affect the tension on the belt in the entire endless system. Accordingly, the need to maintain a proper balance between the first and second systems is readily obvious. Ideally, it is preferable to maintain the weight of the belt portion in the second variable section at a constant level, or at least to within a predetermined relatively narrow range substantially equal to the weight of the belt portion in the first fixed section.
U.S. Pat. No. 4,189,047 to Beckius relates to an endless conveyor wherein the tension of the belt carrying the product cannot be readily adjusted during operation. A progressive counterweight is provided for tensioning the belt where lengthening of the portion of the belt carrying the product automatically reduces the tension force and shortening the belt carrying the product automatically increases the tension force. The amount of weight varies depending upon the vertical positioning of weights and supports within a column 70. German Patent No. 263,275 relates to a conveyor belt tensioner which acts during extreme conditions. Tensioning drum 1 is connected by a tensioning cable 2 to a one-side supported load lever 5, which carries ballast 6. A force created by weights 6 varies depending upon the angle of supported load lever 5.
In present conveyor systems of the type contemplated herein, with belts of relatively small sizes, it has been possible to maintain a reasonable condition of balance between the first and second sections of the take-up section utilizing a fixed weight attached to the dancer roller arm. However, with conveyor belts increasing in width and length, a condition of balance has been more and more difficult to achieve, with the result that belt tension has also become erratic and difficult to control. With additional factors such as sanitary conditions and temperature changes also affecting the systems, prior art endless conveyor systems have been adversely affected in these respects. I have invented a variable counterweighted take-up assembly for an endless conveyor system, and an endless conveyor system having such variable counterweighted take-up assembly which avoids the disadvantages of presently known systems by providing precise control of the amount of supplemental weight added in the variable section of the take-up section of the conveyor system in accordance with specific needs at any time. I have also invented a method of controlling the weight of the belt portion in the second variable section in counterbalance to the first fixed section.
A variable counterweighted take-up assembly for an endless conveyor system is disclosed, the endless conveyor system having a frame, an endless conveyor belt supported by the frame and adapted to traverse a predetermined endless path, and a take-up section wherein excess portions of the conveyor belt are allowed to accumulate so as to permit operational fluctuations in the length of the belt. The portion of accumulated excess belt in the take-up section is divided into at least two adjacent sections, a first fixed section wherein the length and weight of the belt therein is substantially constant, and a second variable section wherein the length and weight of the belt therein is permitted to vary. The first and second sections are opposed to each other in counterbalance relation in a manner to affect belt tension throughout the conveyor system. According to the invention, the take-up section comprises an elongated flexible weighted member having at least two ends, a first end supported by the accumulated belt portion in the second variable section, and the second end supported by a fixed frame member spaced from the second variable section.
Preferably, the elongated weighted member comprises a plurality of individual weight members connected to each other in a manner to permit pivotal articulated movement relative to each other between the second variable section and the fixed frame member so as to permit flexible movement of the weighted member between the second variable section and the fixed frame member in dependence upon variations in the accumulated portion of excess belt in the second variable section. The individual weight members are preferably generally rectangular in shape, and are preferably connected to each other by at least one link chain to permit the pivotal articulated movement relative to each other. Preferably, two link chains are provided, one chain adjacent each of the shorter sides of the rectangular weight members.
The first fixed section and second variable section are preferably positioned within a return section of the conveyor belt wherein the conveyor belt returns from a product discharge station to a product input station while reversing belt direction. The portion of conveyor belt in the first fixed section is in the form of a vertical curtain of belt having an upper and a lower end, and a roller member is positioned at each end for directing the belt along its path within the section. The second variable section is comprised of excess conveyor belt which is directed beneath and around at least a portion of a floating dancer roller so as to assume a generally V-shaped elevational configuration in elevation, whereby the weight of the generally V-shaped excess conveyor belt in the second variable section is opposed in counterbalance relation to the weight of the conveyor belt in the first fixed section, and the elongated flexible weighted member is appended to the floating dancer arm to complement the weight of the excess conveyor belt in the second variable section. The floating dancer arm is permitted to move upwardly and downwardly in dependence upon the amount of excess belt in the second variable section, and the weight of the elongated flexible weighted member is permitted to transfer between the floating dancer arm and the fixed frame member in dependence upon the vertical position of the floating dancer arm as determined by the amount of excess belt in the second variable section.
A substantial portion of the weight of the elongated flexible weighted member is transferred to the floating dancer arm when the excess belt in the second variable section is at a minimum and the floating dancer arm is located at its uppermost vertical portion, and a substantial portion of the weight of the flexible weighted member is transferred to the fixed frame member when the weight of the excess belt in the second variable section is at a maximum and the floating dancer arm is located at its lowermost vertical position. The second variable section communicates with the discharge station of the conveyor belt by a plurality of roller members.
The flexible weighted member is preferably comprised of a plurality of rectangular shaped steel plates and the link chains are preferably bicycle-type link chains having at least one selected link respectively attached to each rectangular shaped steel plate to permit the pivotal articulated movement. The elongated flexible weighted member may also be an elongated unitary flexible member having weight members secured thereto to provide supplementary weight to the flexible member. Alternatively, a unitary flexible member made of a heavy metal such as lead may be provided, weight permitting.
The invention also relates to an endless conveyor system having a variable counterweighted take-up assembly, which comprises a frame, a flexible endless conveyor belt supported by the frame and adapted to traverse a predetermined endless path, a conveyor belt take-up section which permits excess portions of the conveyor belt to accumulate so as to permit operational fluctuations in the length of the belt. The accumulated belt portion is divided into at least two spaced sections, a first fixed section wherein the length and weight of the belt is substantially constant, and a second variable section wherein the length and weight of the belt therein is permitted to vary. The first and second sections are opposed to each other in counterbalance relation in a manner to affect belt tension in the endless conveyor belt. An elongated flexible weighted member has at least two ends, a first end appended to the second variable section, and a second end connected to a fixed frame member spaced from the second variable section.
The conveyor belt traverses a path having an input station and a discharge station communicating with each other by a return section, and the conveyor belt is directed from the discharge station around a plurality of roller members so as to reenter the input station in direction opposite the direction of the discharge station. The take-up section is located in the return section of the conveyor system. The elongated flexible weighted member preferably comprises a plurality of individual weight members connected to each other in a manner to permit pivotal articulated movement relative to each other between the second variable section and the fixed frame member so as to permit flexible movement of the weighted member between the second variable section and the fixed frame member in dependence upon variations in the accumulated portion of excess belt in the second variable section of the take-up section.
The second variable section is comprised of excess conveyor belt which is directed beneath and around at least a portion of a floating dancer roller so as to assume a generally V-shaped elevational configuration, such that the weight of the generally V-shaped excess conveyor belt in the second variable section is opposed in counterbalance relation to the weight of the conveyor belt in the first fixed section. The elongated flexible weighted member is preferably appended to the floating dancer arm to complement the weight of the excess conveyor belt in the second variable section. The floating dancer arm is permitted to move upwardly and downwardly in dependence upon the amount of excess belt in the second variable section, and the weight of the elongated flexible weighted member is permitted to transfer between the floating dancer arm and the fixed frame member in dependence upon the vertical position of the floating dancer arm as determined by the amount of excess belt in the second variable section. It can be seen that a substantial portion of the weight of the elongated flexible weighted member is transferred to the floating dancer arm when the excess belt in the second variable section is at a minimum and the floating dancer arm is located at its uppermost vertical position, and a substantial portion of the weight of the flexible weighted member is transferred to the fixed frame member when the weight of the excess belt in the second variable section is at a maximum and the floating dancer arm is located at its lowermost vertical position. The second variable section communicates with the discharge station of the conveyor belt by a plurality of roller members. The elongated flexible weighted member is preferably comprised of a plurality of rectangular shaped steel plates flexibly connected by one or more link chains of a bicycle-type having at least one selected link respectively attached to each rectangular shaped steel plate to permit the pivotal articulated movement.
The flexible conveyor belt preferably traverses a helical path having a product input station and a product discharge station and the return section communicates the product discharge station and the product input station with each other. The conveyor belt may be adapted to travel in an upward direction along the helical path from the product input station to the product discharge station, or alternatively, the conveyor belt may be adapted to travel in a downward direction along the helical path from the product input station to the product discharge station. Still alternatively, the conveyor belt may be adapted to travel along a straight path between the product input station and the product discharge station and the return section communicates the product discharge station with the product input station. Also, the conveyor belt may be adapted to travel in either of two directions along the straight path.
In the preferred embodiment, an endless conveyor system is disclosed having a variable counterweighted take-up assembly, which comprises a frame, a flexible endless conveyor belt supported by the frame and adapted to traverse a predetermined endless path about a rotating cage, at least a portion of the endless path being helical. A conveyor belt take-up section permits excess portions of the conveyor belt to accumulate so as to permit operational fluctuations in the length of the belt, the accumulated belt portion being divided into at least two spaced sections, a first fixed section wherein the length and weight of the belt is substantially constant, and a second variable section wherein the portion of belt therein extends under and at least partially about a floating dancer roller so as to assume a generally V-shaped configuration. The length and weight of the belt in the second variable section is permitted to vary while permitting the dancer roller to move between the lowermost and uppermost vertical positions in dependence upon the amount of excess belt in the second variable section. The first and second sections are opposed to each other in counterbalance relation in a manner to affect belt tension in the endless conveyor belt. An elongated flexible weighted member has at least two ends, a first end appended to the second variable section, the second end connected to a fixed frame member spaced from the second variable section.
A method is disclosed for controlling excess portions of conveyor belt in an endless conveyor system having a frame, an endless conveyor belt adapted to traverse a helical path about a rotating cage which provides belt driving force by frictional engagement with an inner edge of the belt, a take-up section for receiving excess portions of belt caused by operational fluctuations in the length of the belt, the take-up section being divided into at least two sections, a first fixed section wherein the length and weight of the belt portion therein is substantially fixed, and a second variable section wherein the length and weight of the belt therein is permitted to vary, the first and second sections being opposed to each other in counterbalance relation in a manner to affect belt tension throughout the conveyor system. The method comprises selectively complementing with additional weight, the weight of the portion of belt in the second variable section in a manner to maintain the combined weight therein substantially constant, or at least to within a predetermined range.
The step of complementing the weight of the portion of belt in the second variable section is accomplished by supporting one end of an elongated flexible weighted member by the portion of belt in the second variable section and supporting the other end of the elongated flexible weighted member by a fixed member spaced by a predetermined distance from the second variable section, such that when the weight of the belt portion in the second variable section increases, the amount of complementary weight supported thereby decreases, and when the weight of the belt portion in the second variable section decreases, the amount of complementary weight supported thereby increases.